The flight will provide unique free flight data about hypersonic (faster than Mach 5) air-breathing engine technologies that have large potential pay-offs. The unpiloted 12-foot-long vehicle, part aircraft and part spacecraft, will be dropped from a B-52,aircraft. It will be boosted to nearly 100,000 feet by a rocket and released over the Naval Air Warfare Center Weapons Division Sea Range over the Pacific Ocean off the coast of southern Calif. It will fly under its own power at approximately 5,000 mph.

The $250 million program began with conceptual design and scramjet engine wind tunnel work in 1996. This is the first time a non-rocket, air-breathing scramjet engine has powered a vehicle in flight at hypersonic speeds. No vehicle has ever flown at hypersonic speeds powered by an air-breathing scramjet engine.

In a scramjet (supersonic-combustion ramjet), the flow of air through the engine remains supersonic for optimum engine efficiency and vehicle speed. The rocket boost and subsequent separation from the rocket to get to the scramjet test condition have complex elements that must work properly for mission success. There are few or no moving parts. Achieving proper ignition and combustion, in a matter of milliseconds, proved to be an engineering challenge, but NASA is ready to prove air-breathing scramjets work.

After booster burnout, the 2,800-pound, wedge-shaped research vehicle will separate and fly on its own to perform a preprogrammed set of tasks. After an approximate 10 second test firing of the engine, the X-43A will glide through the atmosphere conducting a series of aerodynamic maneuvers for up to six minutes on its way to splashdown.

Researchers believe these technologies may someday offer more airplane-like operations and other benefits compared to traditional rocket systems. Rockets provide limited throttle control and must carry heavy tanks filled with liquid oxygen, necessary for combustion of fuel. An air breathing engine, like on the X-43A, scoops oxygen from the air as it flies. The weight savings could be used to increase payload capacity, increase range or reduce vehicle size for the same payload.

This is the second flight in the X-43A project. On June 2, 2001, the first X-43A vehicle was lost moments after release from the B-52. Following booster ignition, the vehicle deviated from its flight path and was deliberately destroyed. The mishap investigation concluded there was no single contributing factor, but the root cause of the problem was identified as the control system of the booster.

NASA's Langley Research Center, Hampton, Va., and Dryden Flight Research Center, Edwards, Calif., jointly conduct the Hyper-X program.

A video clip, images and additional information about the project are available on the Internet at:

http://www.nasa.gov/missions/research/x43-main.html

NASA TV will carry the flight and the post-flight news briefing live. NASA TV is available on AMC-9, transponder 9C, C-Band, located at 85 degrees west longitude. The frequency is 3880.0 MHz. Polarization is vertical, and audio is monaural at 6.80 MHz. For information about NASA TV on the Internet, visit:

http://www.NASA.gov/ntv

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